1. FIELD OF THE INVENTION
The present invention generally relates to locking mechanisms and, more particularly, to an improved electromagnetic door lock device.
2. PRIOR ART
There are a large number of different types of electromagnetic door locks, most of which are complicated and expensive to manufacture, install and service and many of which do not perform efficiently. One particular lock as for example is shown in U. S. Pat. No. 4,487,439 which issued on Dec. 11, 1984, to William C. McFadden and entitled Magnetic Shear Locking Methods and Apparatus utilizes a locking mechanism which operates under shear. However, this device utilizes a specially configured electromagnet. When an armature is attracted thereto during locking, a small central tab on the electromagnet extends into a central armature dimple to prevent the armature and the door to which it is attached from moving. Such an electromagnet configuration is expensive to make. Moreover, great care must be made to align the armature and electromagnet, specifically, the central dimple and tab, otherwise the lock will malfunction. Of more importance, consideration shear stress can occur to the electromagnet with resultant cracking and disruption of the electromagnet, particularly if an attempt is made to force the door open while it is in the locked position. Finally, the device is not adapted to a wide variety of applications. Although the electromagnetic door lock device of U. S. Pat. No. 4,826,223 satisfies most of the problems connected with prior art door locks, it still has a problem of properly aligning its electromagnet and movable armature before energizing the electromagnet. Energizing the electromagnet before proper armature alignment can cause improper locking or non-locking of the door.
Accordingly, there is a need for an improved, less expensive, more durable and efficient electromagnetic door locking device which will assure positive door locking and positive armature-electromagnet alignment. Such device should be simple to make, install, inspect, repair and replace. It should also be designed to protect the electromagnet against damage if the lock is forced. In addition, the device should be capable of being utilized for one-way and two-way swinging doors, sliding doors and windows and in applications where the lock is to be connected to the door frame at either the side, top, or bottom of the door.